Born in Norway, but later a US citizen, Gil worked as an engineer for Stutz, then later worked for Revere Motor Company in Indiana. Prior to racing, Gil qualified and worked as a marine engineer. Andersen took pole for the 1912 Indianapolis 500 in an unusual way, as he was the very first entrant for the race, which subsequently earnt him first place at the start. Andersen twice won the National Trophy - in 1913 and 1915 and carried on racing until the end of the 1910's, surviving a big accident in 1916 where he broke his leg.